Numbridge — Strategy

Domains: tempo and blocks

In Domains there is nothing to connect: a block goes to whoever holds five of its nine cells, and the player with more blocks wins. The geometry of bridge links does not apply here at all — what applies is the arithmetic of nines.

A block lives in three states

state of the block      what to do
five cells yours        nothing: it is yours for good, moves here are wasted
five cells theirs       nothing: it cannot be taken back, forget it
4 : 4 or 4 : 3          play here: one cell settles the block
empty or 1 : 1          later: four or five moves of work still needed

The main beginner's mistake is finishing a block you have already won. The fifth cell makes the block yours for good; the sixth, seventh and eighth bring nothing. Every such move is a present in some contested block at the other end of the field.

The second commonest is rescuing a block you have lost. If your opponent holds five there, the block is closed. Nothing you put into it changes the outcome.

A pair of moves is a tool

The order here is 1-2-2: the first player makes one move, and after that each player moves twice in a row. A pair is not doubled tempo but a chance to finish a job in one go, giving your opponent no chance to interfere.

move  1    2  3    4  5    6  7    8  9
who   A    B  B    A  A    B  B    A  A

Two sensible ways to spend a pair:

• Take away and consolidate. With the first move take a cell in a block where your opponent has four; with the second take the fifth cell there for yourself.
• Two different blocks. If one move already settles a block, spend the second in another contested block, not next door.

The bad way is to put both cells into a block that one cell had already settled.

The clock counts each move of a pair separately, and the second move gets its own full limit. But running out of time costs you the whole pair at once: miss the deadline on the first move and there is no second. That is the most expensive clock mistake in the game.

Count blocks left, not cells

The game ends early as soon as one player holds more blocks than the other can reach with every unsettled block added in. So keep the count on the scoreboard: "four for me, three for them, two contested" means one of the two contested blocks is enough for me and they need both. When one is enough, play in the contested block where you are closer; when both are needed, start with the one where your opponent is nearer the fifth cell.

Claiming a given is a normal way of reaching a fifth cell in Domains: a given in a contested block is no worse than a deduced digit and carries no risk of a miss.

Irregular blocks

With jig a block still has nine cells and the majority is still five. The shape changes: a block may stretch across several rows, and a cell that looks as if it lies "in another corner" turns out to belong to it. Do not trust your eye — hover and see which block lights up. On irregular blocks that is exactly what is worth checking before every move.